function process_plot_2d(mesh, pde, U)
x = mesh.node(:,1);
y = mesh.node(:,2);
figure;
unique_x = unique(x);
unique_y = unique(y);
[X, Y] = meshgrid(unique_x, unique_y);
Z = griddata(x, y, U, X, Y, "cubic");
surf(X, Y, Z);
% scatter3(x, y, U, 15, U, 'filled');
colormap('parula');
% colormap('jet');
colorbar;
title(['Example: ', num2str(pde.index)]);
xlabel('x');
ylabel('y');
zlabel('uh');
end